Memory devices are widely used to store information in various electronic devices such as computers, wireless communication devices, cameras, digital displays, and the like. Information is stored by programing different states of a memory device. For example, binary devices have two states, often denoted by a logic “1” or a logic “0.” In other systems, more than two states may be stored. To access the stored information, the electronic device may read, or sense, the stored information in the memory device. To store information, the electronic device may write, or program, the state in the memory device.
Various types of memory devices exist, including random access memory (RAM), read only memory (ROM), dynamic RAM (DRAM), synchronous dynamic RAM (SDRAM), ferroelectric RAM (FeRAM), magnetic RAM (MRAM), resistive RAM (RRAM), flash memory, and others. Memory devices may be volatile or non-volatile. Non-volatile memory, e.g., flash memory, can store data for extended periods of time even in the absence of an external power source. Volatile memory devices, e.g., DRAM, may lose their stored state over time unless they are periodically refreshed by an external power source. A binary memory device may, for example, include a charged or discharged capacitor.
Memory devices typically includes power supply lines throughout the device that provide power from a power supply to the various transistors and other components that are included in the memory. The power supply lines are typically arranged in different metal layers associated with the device. The resistivity of these power supply lines can dissipate power and generate heat as power is transmitted from the power supply. The farther power travels along the power supply lines, the greater this power dissipation and heat generation can be. Additionally, some metal layer have greater resistivity than others. In some cases, lower metal layer have higher resistivity than upper metal layers. Thus, power that is transmitted on power supply lines located in lower metal layers may be more susceptible to dissipation than power that is transmitted on power supply lines that located in upper metal layers.
In order to reduce these power dissipation and heating issues, some memory devices include a redistribution layer that includes low resistivity lines that provide power to certain locations within the device. This layer may be referred to as an “iRDL layer” and may be formed in a semiconductor process that occurs before an assembly process. An iRDL layer may be an uppermost layer of the device, which may be the lowest resistivity layer in the device. In some cases, an iRDL layer is a metal 4 layer (M4) over the metal 3 layer (M3).
In order for power to be transferred from the iRDL layer to lower layers of a memory device, the memory device may include one or more vias, also known as contact plugs. A memory device may include one or more “iRDL vias” that provide conductive pathways between power distribution lines in the iRDL layer (“iRDL lines”) to wiring that is this located in an underlying metal layer. In one example, an iRDL via provides a conductive pathway between a metal 4 layer and a metal 3 layer. The memory device may also include additional vias that provide conductive pathways between other layers, such as M3-M2 vias.
Conventionally, a memory device includes a dedicated area for routing of iRDL vias. These dedicated areas are used to avoid interference with control signals or other wiring that may be present in areas that underlie the redistribution layer. These dedicated areas result in unwanted increases in chip size, power consumption and other disadvantages. Thus, there is a need in the art for improved iRDL via routing.